The present invention relates to an improvement in the process for preparing tetrachloroalkanes from ethylenic hydrocarbons and carbon tetrachloride.
In the preparation of a tetrachloroalkane having more than two carbon atoms from an ethylenic hydrocarbon and carbon tetrachloride, various catalysts for carrying out the reaction in an advantageous manner have been proposed. The methods using the proposed catalysts, however, have merits and demerits, and no satisfactory method has heretofore been developed.
The conventional methods include, for example, (a) a method using an organic peroxide, such as, benzoyl peroxide and di-tertiary-butyl peroxide or an azo compound, such as azobisisobutyronotrile as, disclosed in U.S. Pat. No. 2,440,800, (b) a method using at least one member selected from organic or inorganic salts of metals and amines, optionally in combination with ammonia, metallic iron, EDTA and the like as disclosed in U.S. Pat. Nos. 3,213,149, 3,454,657, 3,651,019 and 3,462,503, (c) a method using a metal carbonyl compound as disclosed in U.S. Pat. No. 3,471,579, and (d) a method using triethyl phosphite and iron chloride in combination as disclosed in Chemical Abstracts, Vol. 75, 1971, 48334n.
The method (a) above is defective in that, since the reaction proceeds very violently and is extremely exothermic, special modifications of the reaction operation and apparatus must be effected so as to have the reaction rate controlled. Even though such modifications have been made, it sometimes is impossible to control the violent reaction, which involves the danger of explosion.
According to method (b), the yield of the product is low especially when the reaction is carried out under a relatively low pressure. Therefore, this method is impractical from the commercial point of view.
The catalyst used in method (c) is toxic and very expensive, and unsuitable for use in large quantities on commercial scale.
The catalyst used in method (d) is very poor in miscibility with carbon tetrachloride, and large quantities of tar-like substances are formed as by-products in the reaction. The tar-like by-products tend to adhere to the inner walls of a reaction vessel or pipings. Therefore, the method is disadvantageous especially when a continuous process is intended for conducting the reaction.